Conventional refrigeration and air conditioning systems utilize a series of recirculating fluid loops to cool a space by transferring the heat from the space, through the fluid loops and ultimately, to a heat sink such as water or ambient outside air. A commercial air conditioning system, for instance, typically includes a water chiller having an evaporator at its low pressure side, a condenser at its high pressure side, a compressor to boost the pressure of refrigerant as it flows from the evaporator to the condenser and an expansion valve to meter refrigerant from the high pressure condenser to the low pressure evaporator.
In a first fluid loop, water passes through the chiller evaporator where it is cooled in a heat exchange relationship with relatively cooler system refrigerant before being directed to a location where it absorbs heat and is returned to the evaporator. In "flooded design" evaporators the water in the chilled water loop flows through the tubes of the evaporator and liquid refrigerant surrounds the outside of the tubes. The cooler liquid refrigerant surrounding the tubes absorbs heat energy from the relatively warmer water, thereby chilling the water.
The liquid refrigerant vaporizes during the removal of heat energy from the warm water in the evaporator. The vaporized refrigerant is pumped out of the evaporator by the compressor which compresses the gaseous refrigerant, raising both its pressure and temperature. The high temperature refrigerant gas then flows to the system condenser where its heat is rejected, most typically, to water in a second fluid loop or directly to ambient air.
As the refrigerant is cooled in the condenser it changes state from a hot gas to a warm, relatively high pressure liquid which is metered, through a pressure reducing expansion valve, to the evaporator. The expansion valve maintains the pressure differential between the high and low pressure sides of the refrigeration system.
The pressure of refrigerant is controllably reduced as it passes through the expansion valve to ensure that the refrigerant will effectively vaporize and absorb heat from the relatively warm water flowing through the evaporator. The cycle is completed, and ready to be repeated, when the liquid refrigerant flows at reduced pressure through the expansion valve back to the evaporator.
The amount of liquid refrigerant introduced into the evaporator should be that amount which can wet the surface area of the tubes of the evaporator without having more or less liquid refrigerant in the evaporator than is needed for a particular cooling load. Accordingly, the expansion valve should be adjustable to control the amount of liquid refrigerant introduced into the evaporator.
In many instances where the cooling load varies on a continuous or near continuous basis, electric, rotary actuated, incrementally adjustable, motor driven, electronically controlled expansion valves are used to continuously modulate the flow of refrigerant into the evaporator in accordance with the changing cooling loads. In other instances, however, the application in which a chiller is employed is such that the rate of refrigerant flow through the expansion valve typically need not change or requires adjustment only at relatively infrequent intervals due to the existence of a very even or near constant cooling load. In such instances, the more expensive, electric motor driven expansion valves, together with the controls necessary for the motor-driven positioning the valve components are not needed or justifiable and comprise an additional expense, complication and potential failure mode with respect to chiller operation.
It is an object of the present invention to provide a rotary, manually operable and adjustable expansion valve of relatively rugged, simple and inexpensive construction.
It is still another object of the present invention to provide a manually operable and durable rotary refrigerant expansion device which is compact so as to take up a minimum amount of space in the refrigerant piping in which it is disposed.
It is a still further object of the present invention to provide a rotary expansion device for a refrigeration system having the capability to permit for the manual adjustment of refrigerant flow through the device in order to meet the requirements of different operating conditions.
These and other objects of the present invention will be apparent from the attached drawings and the Description of the Preferred Embodiment which follows.